Delayed arming fuze for a projectile



April 10, 1956 H. H. DERINGER 2,741,184

DELAYED ARMING FUZE FOR A PROJECTILE Filed Feb. 11, 1946 a Sheets-Sheet 1 2 1% 2. I9 40 38' 34 35 \l\ I I l H E. Berri April 10, 1956 H. H. DERINGER 2,741,184

DELAYED ARMING FUZE FOR A PROJECTILE Filed Feb. 11, 1946 5 Sheets-Sheet 2 4o 38' 34 35 as 34 35 37 I9 P 1956 H. H. DERINGER 2,741,?84

DELAYED ARMING FUZE FOR A PROJECTILE Filed Feb. 11, 1946 s Sheets-Sheet s i z 3. I9 40 34 35 3: 38' 22 I9 40 3a 3.4 35 3| 22 \ll/ I\\lll 'II A 24 2,741,184 7 DELAYED ARMlNG FUZE FOR A PROIECTILE Harry H. Derringer, United States Navy, Chester-town, Md.

Application February 11, 1946, Serial No. 646,942 Claims. (Cl. 10279) (Granted under Title 35, U. S. Code (1952), sec. 266) This invention relates to a safety base fuze for a projectile and more particularly to a fuze for use with a projectile preferably employing the usual nose fuze and adapted to be fired from a gun, the fuze of the present invention being provided with a firing pin adapted to be struck by a percussion cap with sufficient force to explode an explosive charge within the projectile as the projectile strikes the for preventing the premature firing of the explosive charge until the projectile has traveled a safe distance beyond the muzzle of the gun. More specifically, the invention relates to a base fuze for a projectile in which an inertial plunger supporting the percussion cap is maintained in a safe position with respect to the firing pin until the projectile has attained a predetermined speed of rotation during the firing of the projectile from the gun and the force of acceleration of the projectile has diminished to a predetermined value corresponding to an instant position of the projectile ata safe distance from the gun after the projectile has been fired therefrom.

In devices of this character heretofore devised for preventing the premature explosion of the projectile in or within the vicinity of the gun as the gun is fired, it has been the usual practice to employ a pair of cylindrical detents adapted to be moved outwardly within radially disposed tubular apertures within the projectile'and thereby remove a restraint from the firing pin and cause the projectile to be armed as the detents move outwardly to an unlocked position by the centrifugal force acting thereon as the projectile is forced through the bore of the gun by the explosion of the main explosive charge. In the event that the detents should be moved to the unlocked position before the projectile has traveled beyond the muzzle of the gun, the force of acceleration acting on the inertial plunger member may cause the plunger to strike the firing pin with sufiicient force to explode the projectile while the projectile is still within the barrel of the gun thereby damaging or destroying the gun and causing casualties to the gun crew and other personnel within the vicinity of the gun.

In accordance with the present invention this difiiculty is overcome by employing a pair of locking detents in which the outer cam surfaces thereof coact with complementary cam surfaces of a pair of annular inertia members sufiiciently to prevent movement of the detents outwardly to an unlocked position as the gun is fired until the force of acceleration of the inertia members within the projectile has decreased sufliciently to permit such movement.

One of the objects of the present invention is the provision of new and improved means for preventing the premature firing of an explosive charge within a projectile during the transportation, handling, loading and firing of the projectile from a gun in which the projectile is armed during flight and remains armed until the projectile explodes upon impact with a target.

Another of the objects is to provide new and improved target, in which means are employed 2,741,184 Patented Apr. 10, 1956 means for maintaining the inertial plunger of a fuze for a projectile locked in a safe position as the projectile is fired from a gun until the acceleration of the projectile has decreased suflicientlyto permit movement of a pair of detents from an initial locking position in which means are provided for retarding the additional movement of the detents as the detents move toward a release position.

Another object is to provide a new and improved device for preventing the premature firing of an explosive charge within a projectile in which the inertial plunger is maintained in a safe position until the velocity of the projectile has reached substantially the maximum value after being fired from a gun and in which the safety means are maintained locked by a pair of annular inertia members adapted to be moved to locked position by the force of acceleration during the travel of the projectile through the gun.

A further object is to provide a new and improved device for maintaining the percussion cap of a projectile, in a safe position with respect to the firing pin until the projectile is shot clear of the gun which is economical to manufacture, reliable in operation and which possesses all of the desired qualities of ruggedness and durability.

Still other objects and advantages will be apparent from the following description, taken in connection with the accompanying drawings, of which:

Fig. l is a view in elevation and partially in section of a projectile employing the device of the present invention according to a preferred embodiment thereof;

Fig. 2 is an enlarged fragmentary sectional view taken on line 22 of Fig. 1;

Fig. 3 is an enlarged fragmentary sectional view of one of the locking detents and inertia members employed with the device of Fig. 1 showing the detent momentarily maintained in an initial locked as the projectile travels through the bore of the gun;

Fig. 4 is a view similar to Fig. 3 but showing the locking detent and inertia member maintained in the unlocked or released position by centrifugal force as the projectile travels along a trajectory and strikes a target.

Fig. 5 is a view in diagrammatic form of the device in safe condition and showing in dashed outline the explosive train interrupted;

Fig. 6 is a diagrammatic view similar to Fig. 5 but showing the device in a fired condition with the explosive train continuous;

Fig. 7 is a fragmentary sectional view partly broken away of an alternative form of the invention; a

Fig. 8 is a view similar to Fig. 7 but showing the locking detent maintained in an initial locked position by the inertia member as the projectile travels through the bore of the gun;

Fig. 9 is a view similar to Fig. 8 but showing another locking position of the detent and inertia member;

Fig. 10 is a view of the device of Fig. 7 showing the locking detent momentarily restrained by the inertia member as the projectile strikes a target;

Fig. 11 is a view of an inertia member similar to the inertia member of Fig. 2 and a modified form of detent employed therewith; and

Fig. 12 is a view of a detent similar to the detent of Fig. 11 and another modified form of inertia member suitable for use therewith.

Referring now to the drawings for a more complete understanding of the invention and more particularly to Fig. 1 thereof, there is shown thereon a projectile indicated generally by the numeral 10 having an annular recessed portion 11 therein adapted to be engaged by a complementary portion of an explosive filled shell to which thev projectile is secured, as is well known in the art to which the present invention pertains. The projectile is also position by the inertia member *ovided, with an annular sleeve 12 of material suitable r the purpose such, for example, as brass adapted to be lgaged by the rifiing of the gun as the projectile is pro- :lled outwardly therefrom by the firing of the explosive large within the aforesaid shell andthereby impart a vtary movement to the projectile about the axis thereof the projectile moves through the boreof the gun. The ojectile is thus, adapted to be propelled along a predermined trajectoryand to spin or rotate continuously .roughout the trajectory. v

The projectile 10 comprises a shell 13, the forward end lereof having secured thereto in any suitable manner a use 14 in which is preferably arranged the usual nose ze 15 The shell 13, comprises a rear wall 16 integrally armed therewith in which a screw-threaded opening 17 'is rovided for receiving and supporting the base fuze gen- 'ally indicated by the reference character 18. The base ze comprises a housing 1-9. composed of any suitable raterial for the purpose, the forward end thereof being d as at 2 or e ng. an u port n e us a lock member 22. The block'memberis provided with a :cess 23 in the forward end thereof having a booster 1arge;24 arranged therein, the booster charge being re LiIlCd within the recess 23by a flange member 25.

Secured Within the member 22 as at 26 is a firing pin 7 such that the firing pin is in axial alinement with the rojectile. The member 22 is provided with a pair of dialetrically arranged apertures 28 within which is disposed pair of locking detents 29 adapted to be releasably maintined in engagement with the reduced cylindrical portion of the firing pin by a pair of springs 31, the springs eing arranged to urge the detents 29 yieldably' and in- 'ardly against the firing pin.

A pair of cylindrical chambers 32. communicates in ligned relation with each of the apertures 28 respecvely, the chambers being of sufficient size to permit the nnular inertia members 33 to move radially therein, as ill, more clearly appear as the description proceeds. The hambers, 32are closed at one end thereof by disks 34 aving formed thereon reduced extensions 35 about which resprings 31 are arranged, the springs being disposed etween the inner surface ofidisk members 34 and inner lalls 36, of the detents 29. whereby the detents are yieldbly and inwardly urged against the reduced cylindrical ortion 30 of the firing pin 27, Fi'gs. 2 and 5. The disks 4 areheld in fixed position within theblock member 22 [1 any suitable manner as by crimping at 40.

The locking detents 29 are respectively provided with onical cam surfaces 37- adaptedto engage complemenary conical cam surfaces 38 provided on the inertia memiers33 thereby to limit the outward movement of the letents until the projectile has passed beyond the muzzle )f the gun. The inertia members 33', it wil1'-be noted,.are 1150 provided with conical cam surfaces designated for theiurpose of description by the numeral 38 and formed dentical with the cam surfaces 38 whereby the inertia members may be assembled at random within their re- :pective recesses 32 without the possibility of failure of he device through improper assembly. With the detents 29 in the position shown on Figs. 2 and of the drawings, :he usual fuze plunger 39 is maintained in safe-or unarmed Josition and prevented frornbeing moved into the firing position with respect to the firing pin by the respective portions of the detents which extend inwardly beyond aper- :ures 2 8 and engage the firing pin.

As shown on Figs. 2, 4, and 6 of the drawings, the plunger 39 has secured in the forward end'thereof a percussion cap 41 which is adapted to be moved forward therewith and strike the firing pin with sufiicient force to cause the cap to fire as the projectile strikes the target. The plunger is normally maintained in the safe position out of engagement with the detents 29 by a spring 42, a portion of which is shown on Fig. 2 of the drawings, further detailed description and showing thereof being deemed unneces- 4 sary as this arrangement is well known to those skilled in the art.

With'the projectile at rest, as shown on Figs. 2 and 5, the plunger 39 supporting the percussion cap 41 is maintained in a safe position and prevented from being moved into contact with the firing pin 27 by the locking detents 29. It will be understood, however, that when the projectile is at rest, the explosive train 43 shown within the plunger 39 in dashed outline, Fig. 5, and the explosive train 44 shown in dashed outline in the block 22 are interrupted with respect to each other and thus the fuze remains ineffective to fire the main explosive charge until it has been fired from the gun and strikes the target.

It will also be understood that the, inertial plunger 39 is normally spaced a predetermined distance from the firing pin 27 and maintained in spaced relation therewith by the aforesaid spring 42, the detents 29 preventing the plunger from engaging the firing pinuntil. the detents are moved to the armed or unlocked position by centrifugal force.

Fig. 6 show in diagrammatic form the device in a firing position with the detents 29 moved outwardly to the unlocked position thereof at the moment of impact of the projectile with ajtarget.

It will be understood, however, that as the projectile is propelled along the bore of the gun by the explosive blast, the rifiing of'the bore of the gun engages the sleeve 12 and imparts rotative movement to the projectile thereby causing the detents 29 to move outwardly in accordance with the law of centrifugal forceapplied to rotating masses. This forceis of su'lficient strength to overcome the tension in the springs 31 and the setback force applied to the inertia members 33 and thereby cause the detents to move outwardly to an armed or released position clear of the path of travel of the plunger 39. thus permitting the plunger to strike the firing pin 27 and fire the percussion cap 41 and explode the projectileupon impact of the projectilewith the target.

As shown diagrammatically in Fig. 6 of the drawings, upon. impact of the projectile with the target the plunger 39 is moved forwardly againstthetension of the spring 42 and the explosive train 43 therein is broughtin registration with the explosive train'44 thereby providing a continuous explosive train 43-44 extending from the percussion cap 41 to the booster charge 24.

As the projectile travels through the bore of the gun in response to the firing of the gun, the inertia members 33 are continuously urged rearwardly by the force of acceleration applied. thereto and thus engage the rear walls of the chambers 32, the detents being maintained in the locked position by the inertia members meanwhile thereby preventing the plunger 39 from striking the firing pin until such acceleration has been reduced to a predeter minedsmall value sufiicient to permit the centrifugal force to move the detents to the position shown in Fig. 4. The force resulting from the acceleration of the projectile in response to the expansion of the gases within the gun is applied in a direction along the path of travel of'the projectile and is therein referred to as a setback force. This setback force decays rapidly as the projectile leaves the muzzle of the gun and attains zero value when the maximum velocity of the projectile is reached.

It will be readily understood from an'inspection of the arrangement of thelvarious parts of Fig. 3 that during the travel of the projectilethrough the bore of the gun the setback force predominates the centrifugal force and thus further outwardmovement of the detents 29 from the position thereof illustrated is prevented at this time by the engagement of the cam surfaces 37 and 38 respectively arranged onthe detents and inertia members whereby the plunger-39 is prevented from being moved into engagement with the firing pin 27 until the setback force has decreased sufficiently to permit movement of the detents to the released or armed position thereof. It will be understood, however, that the detents 29 are maintained in the locked or safe position by the inertia members 33 and will remain in such position until the projectile has moved a safe distance beyond the muzzle of the gun, at which time the setback force has diminished sufiiciently such that the centrifugal force will come in play and urge the detents outwardly into the armed position shown on Figs. 4 and 6.

As the gun is first fired, the initial movement of the projectile away from the shell is a motion of translation and when the projectile has moved a predetermined distance within the bore of the gun, the sleeve 12 engages the riding of the bore and rotation of the projectile is initiated thereby. From the foregoing, it will be apparent that the setback force is applied to the projectile prior to the rotative movement thereof and thus the inertia members 33 are moved rearwardly by setback force and effectively lock the detents 29 in the path of travel of the plunger 3? before the centrifugal force comes into play, thereby providing an arrangement in which there is no possibility of prematurely arming the projectile until the projectile has safely cleared the gun and the setback force has decreased to a value suificient to permit the movement of the inertia members to an unlocking position in response to a side thrust applied thereto by the locking detents.

On Figs. 7 to is shown an alternative form of the device in which the movement of the detent from an initial locking position to the unlocking position thereof is delayed momentarily and in which means are provided for momentarily restraining any movement of the detent toward the locking position thereof as the projectile strikes the target. In this form of the device the detent 45 is provided with an annular groove 46 adapted to have locking engagement with the annular rib 47 on the inertia member 43. An arrangement is thus provided in which the detent is maintained in the locking position with respect to the plunger 3? by the inertia m mber 48 as the projectile is fired from the gun by reason of the cam surfaces 37 and 38 on the detent and inertia member respectively being brought into mutual engagement in response to the setback force applied to the inertia member 43 and the centrifugal force applied to the detent. When the setback force has decreased suihciently for the inertia member to be forced forwardly by the detent 45 in response to the centrifugal force applied to the detent, the detent moves toward the unlocking position until the conical surface 37 thereof engages the annular rib 47 of the inertia member, Fig. 9. It will be understood that sufiicient setback force is present at this instant to cause the inertia member to be moved to the position shown on Fig. 9 and thereby retard the movement of the detent toward the unlocking position for a period of time controlled by the setback force applied to the inertia member. The setback force, it will be readily understood is decreas' ing with the travel of the projectile along the trajectory and thus the detent moves to the unlocking position with respect to the plunger 39 when the setback force applied to the inertia. member has decreased to a predetermined value. From the foregoing it will be apparent that the device of Fig. 7 is similar to the device of Pig. 2, the device of Fig. 7 having the additional advantage of delaying the time in which the detent moves from the initial locked position to the unlocked position thereof, and thus the projectile becomes armed at a greater distance from the muzzle of the gun during the flight of the projectile.

In addition to the foregoing the device of Fig. 7 possesses the advantage of momentarily locking the detent in the retracted or armed position thereof as the projectile strikes the target whereby there is no possibility of interference with the movement of the plunger toward the firing pin in response to the impact of the projectile against the target even under the most adverse conditions. The manner in which this is accomplished will best be understood by reference to Fig. 10 in which the inertia member 48 is quickly forced forward into the locking position with V 63 respect to the annular groove 46 of the detent by the set forward force applied to the annular member as the pro: jectile strikes the target, and thus the detent is momentarily restrained in the retracted or armed position for a period of time greatly in excess of the time required for the plunger to strike the firing pin.

On Fig. 11 is shown an alternative form of detent suit able for use with the arrangement of Fig. 2 in which the detent is momentarily restrained in the armed position as the projectile strikes the target. In the specific form of the invention shown on Fig. 11 the detent is designated 53 and comprises a conical cam surface 50 adapted to engage a complementary cam surface 51 or 51, as the case may be. As the detent 53 moves outwardly by centrifugal force to the unlocking position, the groove 54 formed on the detent 53 is employed to restain the detent momentarily during movement thereof to the unlocked position by engagement with the portion 55 of the inertia member 59 as the inertia member is moved forwardly by the setforward force at the moment of impact of the projectile with the target.

On Fig. 12 of the drawings a still further modified form of the device is shown, the device comprising an inertia member designated generally by the numeral 56 having a pair of identical cam surfaces Eli-57, either of which is adapted to engage a conical cam surface 58 provided on the detent 5% thereby to prevent outward movement of the detent to the unlocking position thereof until the projectile has safely cleared the muzzle of the gun. The inertia member 56, it will be understood, is also provided with a plurality of annular grooves 61 adapted to be brought into interlocking engagement with the annular rib 62 provided on the detent 59 whereby the outward movement of the detent toward the unlocking position thereof is retarded by engagement of the annular rib 62 with the grooves 61 in succession as the inertia member 55 is urged rearwardly by the setback force applied thereto which, it will be understood, has decreased sufficiently to permit such outward movement of the detent in response to the centrifugal force applied thereto.

The cam surface 5"! is employed to coact with the annular rib 62 and momentarily restrain the detent in the unlocked position as the projectile strikes the target.

While the invention has been described with particularity in reference to the several embodiments disclosed which produce satisfactory results, it will be apparent to those skilled in the art to which the invention pertains, after understanding the invention, that the invention in its broader aspect could be carried out by other instrumentalities, and it is understood that the terms used in the claims are words of description and not of limitation except as necessitated by the prior art.

The invention herein described and claimed they be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patient of the United States is:

1. In an arming device for a projectile having an explosive charge therein, a casing secured to one end of said projectile for supporting said arming device therein, a firing pin secured within said casing, an inertial plunger slideably arranged within said casing and having a percussion cap secured thereto and adapted to strike said firing pin and explode said explosive charge as the projectile strikes a target, a pair of hollow detents slideably arranged within said casing and adapted to be moved radially outward to an armed position by centrifugal force as the projectile rotates, a pair of springs respectively ar ranged in said hollow detents for yieldably urging the detents into engagement with said firing pin thereby to lock the inertial plunger in an unarmed position until after the projectile has moved a predetermined distance beyond the muzzle of the gun, means secured to said casing for applying a predetermined pressure to said springs, a pair of 7 nnular inertia members movably arranged within said asing and adapted to enclose a portion of the detents then the detents have been moved to said armed position,- nd means respectively arranged on said inertia members nd adapted to be engaged by complementary means aranged on said detents for preventing movement of the etents to said armed position until the setback force has een reduced to a predeterminedvalue and substantially 1e maximum velocity of the projectile has been attained.

2. In a safety device for a projectile having an explosive harge therein, a cylindrical casing secured to one end of he projectile and extending interiorly therein for support- 1g said device, a firing pin secured within said casing in oaxial relation therewith, an inertial plunger slideably rranged within said casing and having a percussion cap. ecured therein in predetermined spaced relation with espect to said firing pin when the projectile is at rest, a air of detents movably arranged within said casing and ,dapted to be moved outward to an armed position by entrifugal force when the projectile has been fired from gun, said detents having a pair of conical cam surfaces espectively formed thereon, means for yieldably urging he detents into abutting relation with the firing pin while he projectile is at rest, a pair of annular inertia members 1rranged within said casing and adapted to be shifted earwardly in response to the setback force applied thereto ,s the gun is fired, a pair of circular complementary cam urfaces respectively arranged on said inertia members 1nd adapted to be engaged by said conical cam surfaces hereby to prevent movement of the detents to said armed losition until the setback force has been reduced to a preletermined value and substantially the maximum velocity 7f the projectile has been attained, and a pair of annular ibs respectively formed within the annular inertia memwers and having cam surfaces thereon adapted to engage aid conical cam surfaces on the detents thereby to reard said outward movement of the detents to said armed )osition until the projectile has traveled a predetermined listance from the gun.

3. in a safety device for a projectile having an explosive :harge therein, a cylindrical casing secured to one end of he projectile and extending interiorly therein for supaorting said arming device, a firing pin secured within :aid casing in coaxial relation therewith, an inertial lunger slideably arranged within said casing and having percussion cap secured therein in predetermined spaced elation with respect to said firing pin when the projectile s at rest, a pair of detents movably arranged Within said :asing and adapted to be moved outward to an armed )OSi'tlOIl by centrifugal force when the projectile has been ired from a gun, said detents having a pair of conical :arn surfaces respectively formed thereon, means for ieldably urging the detents into abutting relation with he firing pin while the projectile is'atrest, a pair of tnnular inertia members arranged within said casing and adapted to be shifted rearwardly in response to the setback force applied thereto as the gun is fired, a pair of circular :ornplementary cam surfaces respectively arranged on the inertia members and adapted to be engaged by said :onical cam surfaces thereby to prevent movement of the. :letents to said armed position until the setback force has seen reduced to a predetermined value and substantially he maximum velocity of the projectile ha been attained, pair of annular ribs respectively formed within the annular inertia members and having cam surfaces thereon adapted to engage said conical cam surfaces on the detents thereby to retard said outward movement of the detents to said armed position until the projectile has traveled a predetermined distance from the gun, and a pair of nnula roo s espe ti ly e n. Said tent nd adapted to be engaged by said annular ribs on the inertia. members and momentarily lock thedetents inthe armed position when the inertia, members are shifted forwardly by the sctforward force as the projectile strikes a target.

4. in a safety device for a projectilezhaving an explosive charge therein, a cylindrical casing secured to one end of the projectile and extending interiorly therein for supporting said device, a firing pinv secured within said casing in coaxial relation therewith, an inertial plunger r arranged within said casing and having a percussion cap secured therein in a predetermined spaced relation with respect to said firing pin when the projectile is at rest, a pair of detents having annular ribs formed thereon and movably arranged within said casing in normal abutting relation with respect to said firing pin and adapted to be moved outward to an armed position by. centrifugal force, means for yieldably urging said detents into said abutting relation with the firing pin when the projectile is at rest, a pair of inertia members respectively arranged within said casing and adapted to be shifted in response, to the setback. force applied thereto as the gun is fired, a pair of complementary cam surfaces respectively arranged on the inertia members and adapted to be engaged by said complementary cam surfaces thereby to. prevent movement of the detents to said armed position until the setback force applied thereto had been reduced to a predetermined value and substantially the maximum velocity of the projectile has been attained, and a plurality of grooves formed within the inertia members and adapted to engage said annular ribs on the detents thereby to retard the outward movement thereof to said armed position until the projectile has traveled a predetermined distance from the gun.

5. An arming device for a projectile comprising a casing supported on one end of the projectile and having an inertial plunger slideably arranged therein, a pair of centrifugally responsive hollow detents slideably arranged within said casing normally in the path of said plunger for preventing movement of said plunger'until the detents have been moved radially and outwardly by centrifugal force as the projectile rotates, resilient means respectively arranged within said hollow detents for yieldably urging the detents inwardly in said path of travel of the plunger until the projectile has moved a predetermined distance beyond the muzzle of a gun after being fired therefrom, a pair of annular inertial members normally in concentric alignment with said detents and constructed and arranged to be moved rearwardly by setback force applied thereto as the projectile is fired from the gun, a pair of conical cam surfaces respectively formed on said detents, and a pair of circular complementary cam surfaces respectively formed on the inertial members normally out of engagement with said conical cam surfaces on the detents and constructed and arranged to engage said conical cam surfaces as the annular member moves rearwardly in response to said setback force applied thereto.

References Cited in the file of this patent 

